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WxWatcher007

2020 Atlantic Hurricane Season Tracking Thread

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Tropical season has kicked off with our first named storm.

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Tropical Storm Arthur Discussion Number   2
NWS National Hurricane Center Miami FL       AL012020
1100 PM EDT Sat May 16 2020

An Air Force Reserve reconnaissance aircraft that has been
investigating the tropical cyclone east of Florida has recently
found maximum 925-mb flight-level winds of 45-46 kt to the
southeast and east of the center, which equates to surface winds
of 34-35 kt, along with uncontaminated SFMR surface wind speeds of
33-36 kt. Based on these data, the depression has been upgraded to
Tropical Storm Arthur, the first named storm of the 2020 Atlantic
hurricane season.

The initial motion estimate remains north-northeastward or 030/11
kt. Arthur made a slight northeastward jog earlier this evening,
but now appears to have returned to its previous base course. A
motion toward the north-northeast is forecast to continue for the
next 24 hours or so, keeping the cyclone well offshore the coasts
of Florida and Georgia. A sharp shortwave trough currently moving
across the southern Plains is forecast to dig east-southeast to
southeastward over the next 48 hours, which will act to accelerate
and eject Arthur more poleward. The more the shortwave trough digs
and loses latitude, the more Arthur could get pulled closer to
the North Carolina Outer Banks as per the GFS and HWRF scenarios.
In contrast, the ECMWF and UKMET models show the shortwave losing
amplitude quickly and lifting out, which acts to push Arthur
farther away from the United States east coast. For now, the new
NHC forecast track closely follows the various consensus models,
which are about midway between the GFS-HWRF and ECMWF-UKMET
solutions. However, the track was adjusted slightly to the right of
the previous advisory track due mainly to the more eastward initial
position. It should be noted that forecast track uncertainty is 
typically larger for weak systems like Arthur.

Arthur has moved off of the warm waters of the Gulfstream current
and currently is passing over a cold pool with SSTs near 24.5 deg
C. These cooler waters should prevent any significant strengthening
in the very near term. By 24 hours however, the cyclone is forecast 
to pass back over the warmer waters of the Gulfstream while moving 
into a very low vertical wind shear regime. These conditions, 
coupled with some cooler air aloft, should allow more vigorous 
convection to develop near the center, resulting in more 
strengthening as Arthur passes near the North Carolina coast. 
Extratropical transition should occur in about 48-60 hours over the 
much cooler waters of the North Atlantic. The NHC intensity 
forecast follows a blend of the consensus models HCCA and IVCN, and 
is similar to the previous intensity forecast.

Key Messages:

1. A tropical storm watch is in effect for a portion of the
North Carolina coast.  Tropical-storm-force winds and heavy rains
are possible there on Monday.

2. Dangerous coastal surf conditions and rip currents are expected
to spread northward from Florida to the mid-Atlantic states during
the next few days.  See products from your local National Weather
Service Forecast Office for more details.


FORECAST POSITIONS AND MAX WINDS

INIT  17/0300Z 29.4N  77.7W   35 KT  40 MPH
 12H  17/1200Z 30.5N  77.2W   35 KT  40 MPH
 24H  18/0000Z 32.2N  76.4W   40 KT  45 MPH
 36H  18/1200Z 34.1N  75.2W   45 KT  50 MPH
 48H  19/0000Z 36.2N  73.0W   45 KT  50 MPH
 60H  19/1200Z 37.5N  70.6W   50 KT  60 MPH...POST-TROP/EXTRATROP
 72H  20/0000Z 38.0N  69.1W   50 KT  60 MPH...POST-TROP/EXTRATROP
 96H  21/0000Z 38.0N  67.6W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  22/0000Z...DISSIPATED

$$
Forecaster Stewart


 

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Arthur is still the main show but our active period relative to the time of season is likely to continue. A very strong CCKW is forecast to reach the EPAC/ATL by the end of the month. Given the SSTs, I’d favor homebrew in the Caribbean/SW Atlantic if things break toward a trigger being in the region. 

First two images courtesy of Eric Webb

fxRs90c.png
 

3usfANM.jpg
The basin is still not ready for prime time, so when the wave passes I think we’re quiet for a while but things are simmering in the Caribbean as the 3.4 region continues to cool dramatically. 

Cs4vlmI.png
 

VSChrBL.png

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2 hours ago, WxWatcher007 said:

Arthur looking better this morning with that burst of convection near the center. Rain extending into SE VA.

We've been dry for about 10 days straight prior to Arthur. This was an over performer in my area of North Carolina as relates to precipitation amounts. Nice and gusty too but nothing more than an average storm. Much needed for lawns. 

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17 minutes ago, Stormpc said:

We've been dry for about 10 days straight prior to Arthur. This was an over performer in my area of North Carolina as relates to precipitation amounts. Nice and gusty too but nothing more than an average storm. Much needed for lawns

Good to hear. It’s crazy how much rain has fallen this year in other parts of the south.

Recon found another pressure drop. Nice storm to watch from afar.

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Getting some steady light rain in the northern neck from the outter bands this afternoon. Pretty cool to get tropical this early.

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4 minutes ago, WxWatcher007 said:

Good to hear. It’s crazy how much rain has fallen this year in other parts of the south.

Recon found another pressure drop. Nice storm to watch from afar.

We were saturated with rain until about May 7th. Then it got cold then dry so much that the Bermuda that started to wake up earlier this month stopped growing

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Looks like the GFS is getting on board with some of the other forecasts of tropical cyclogenesis at the beginning of June.

gfs_mslp_pcpn_watl_fh276-300.thumb.gif.7e6d66ba3a2d13ece78ef91ddd0197b7.gif

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1 hour ago, cptcatz said:

18z GFS is getting even more aggressive 

gfs_mslp_pcpn_seus_fh288-312.gif

End of the month/Early June is definitely a period to watch. As that strong CCKW passes through I expect development in either the Atlantic or EPAC. 

Caribbean would be a prime spot for development if shear isn’t awful. SW Atlantic could work but SSTs aren’t really that great. Arthur was able to thread the needle.

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NOAA will upgrade the hurricane-specific Hurricane Weather Research and Forecast system (HWRF) and the Hurricanes in a Multi-scale Ocean coupled Non-hydrostatic model(HMON) models this summer. HWRF will incorporate new data from satellites and radar from NOAA’s coastal Doppler data network to help produce better forecasts of hurricane track and intensity during the critical watch and warning time frame. HMON will undergo enhancements to include higher resolution, improved physics, and coupling with ocean models. 

As the hurricane season gets underway, NOAA will begin feeding data from the COSMIC-2 satellites into weather models to help track hurricane intensity and boost forecast accuracy. COSMIC-2 provides data about air temperature, pressure and humidity in the tropical regions of Earth — precisely where hurricane and tropical storm systems form.

Also during the 2020 hurricane season, NOAA and the U.S. Navy will deploy a fleet of autonomous diving hurricane gliders to observe conditions in the tropical Atlantic Ocean and Caribbean Sea in areas where hurricanes have historically traveled and intensified.

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This is a fantastic illustration of why I think development is increasingly likely in June. Shear drops like a rock and we get better lift in the part of the basin with the best SSTs and TCHP. 

Just need a trigger, and the CAG may be it. 

 

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Been tracking all day lol. There’s a brief window for 91L to organize and develop before coming ashore in SC or NC. It has gradually organized today but there is still a ways to go. Moisture eventually gets to the region. 

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1 hour ago, WxWatcher007 said:

Been tracking all day lol. There’s a brief window for 91L to organize and develop before coming ashore in SC or NC. It has gradually organized today but there is still a ways to go. Moisture eventually gets to the region. 

Maybe that trajectory around the ATL ridge will become a theme this season....:weenie:

 

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Alright, let’s do a deeper dive into 91L. 

Earlier today, the area of disturbed wx over Florida which has brought significant flooding moved offshore. As that occurred, a weak surface low formed. This low was just east of Orlando, and was decoupled from a more vigorous mid level vortex further offshore. Importantly, the convection has been aided by enhancement on the downshear side of an upper level trough.

80074903.gif?0.2070577052802789


The surface low is offshore, and how far east it gets is critical as it’d put the low under the Gulf Stream. It was just a few days ago where Arthur was able to take advantage of this warm ribbon of SSTs to develop into a tropical storm.
sfcplot_91L_latest.png

cdas-sflux_sst_watl_1.png

Odds of development increased, as we saw persistent convection and vortex stretching near hot towers. This creates a more favorable environment for a surface low to redevelop under the deeper convection nearer the mid level center. 

88437410.gif?0.44597676207309267

This evening, we still see convection continue and some evidence per late day visible imagery that the LLC is trying to couple/redevelop under the MLC.

27777802.gif?0.7764159266723648
 
Now, there’s still a lot of disorganization. If this were August, I’d be all aboard, but given the proximity to land and presence of strong wind shear 91L will need to thread the needle.

wg8shr.GIF

Tonight we need to see development further east to see increased SSTs and more time over water really get things going. 

There is a very short window for sufficient organization for tropical cyclone (TC) genesis. Maybe 12-18 hours. I put odds at 40%.

Regardless, rain should make it to the region this week. It’s unclear if the heavier rain is west or more centered over the metro area. 

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When I’m up early you know it’s gettin good.

91L looks like it organized further east (good job GFS) and is making a legitimate run at classification. Still not the best looking, but convection looks more organized around the apparent center and there are at least a few hours to go before landfall in SC. The apparent center is now visible on CLX radar and shows evidence of an organizing center. 

29103947.gif?0.4654590946360242
 

kkX5j1X.jpg

I think I’d put the odds at 60% for TC genesis.

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Absolutely fascinating to watch. Another tower going up near the center. If it can keep this up and wrap convection around the nascent center it’ll be our second named storm of the season.

32186043.gif?0.740331497194356

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Alright, we have a lot going on this morning as 91L makes a run at becoming a named storm. There’s not a lot of time, but things are organizing at an increasingly rapid clip IMO.

xzZ1DDk.jpg
 

Above I circled the core. Notice how it is MUCH more well defined than it was in my earlier image. To my untrained eye, there’s even evidence of curved banding in the center, which speaks to this becoming organized and capable of sustaining convection. It’s not fully wrapped of course, so this limits whatever intensification could take place but it looks like textbook TC genesis. 

ChDLmH9.jpg

Here’s the wind response aloft. Now I picked the best pixel lol, but winds have increased to 50-60 mph above the surface. Bouy reports gusts to 43 mph. 

The inner organization alone suggests that this is a tropical storm.
 

WOW at the latest radar image. 

nnLh64p.jpg

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